Method to generate microcapsules with hexahydrotriazine (HT)-containing shells

ABSTRACT

Materials and methods for preparing a payload-containing microcapsule with walls that have hexahydrotriazine (HT) and/or hemiaminal (HA) structures are disclosed. To an HT small molecule or a HA small molecule, or a combination thereof, in a solvent is added a cross-linking agent, NH4Cl, and a copolymer. The solution is acidified, and a payload agent is added. The HT small molecule and HA small molecule may have orthogonal functionality.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 15/465,252, filed Mar. 21, 2017. The aforementioned relatedpatent application is herein incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

Materials and methods described herein relate to encapsulated payloads.

BACKGROUND

Microcapsules may be used as release systems for various types ofmaterials (also referred to as “payloads”). Examples of payloads mayinclude perfume oils, repellants, self-healing agents, or disinfectingagents, among other alternatives. Rupturing the microcapsule, andrelease of the payload, may depend on mechanically breaking a polymershell of the microcapsule. For example, the polymer shell may be brokenby scratching, puncturing, or other mechanical means directly applied toa polymeric surface of the microcapsule.

SUMMARY

Embodiments described herein relate to methods of making microcapsulesthat have hexahydrotriazine (HT), hemiaminal (HA) functionality, or acombination thereof.

According to one embodiment, a method of making microcapsules isprovided. The method includes forming a mixture comprising ahemiaminal-based compound, a cross-linking agent, a copolymer, and asolvent; acidifying the mixture; and adding a payload agent.

According to another embodiment, a method of making microcapsules isprovided. The method includes forming a mixture comprising anorthogonal-functionalized hemiaminal small molecule, a cross-linkingagent, NH₄Cl, a copolymer, and a solvent, the orthogonal-functionalizedhemiaminal small molecule comprising the structure

wherein X′ and X″ are each independently selected from the groupconsisting of —OH, —O—, —NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂,—OR², and —R³, and combinations thereof, wherein R¹, R², and R³independently comprise at least 1 carbon; acidifying the mixture; andadding a payload agent.

According to another embodiment, a microcapsule is provided. Themicrocapsule comprises at least one hexahydrotriazine-based compound,hemiaminal-based compound, or a combination thereof; and at least onecomponent covalently linked to the hexahydrotriazine-based compound,hemiaminal-based compound, or a combination thereof, the at least onecomponent comprising the structure

wherein X′ and X″ are each independently selected from the groupconsisting of —OH, —O—, —NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂,—OR², and —R³, and combinations thereof, wherein R¹, R², and R³independently comprise at least 1 carbon.

Features and other benefits that characterize embodiments are set forthin the claims annexed hereto and forming a further part hereof. However,for a better understanding of the embodiments, and of the advantages andobjectives attained through their use, reference should be made to theDrawings and to the accompanying descriptive matter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an example of the formation of a microcapsule having anencapsulated payload.

DETAILED DESCRIPTION

The present disclosure relates to the formation of microcapsules havingan encapsulated payload. In the present disclosure, the payload isincorporated into a nanocapsule or microcapsule with a polymeric wallthat has HT moieties, HA moieties, or a combination thereof. The HT andHA moieties may have additional orthogonal functionality, which wouldallow for covalent bonding of other moieties to the polymer matrix (alsoreferred to as a “polymer shell”). After incorporation into a polymericmatrix, an end user can rupture the capsules by various means, includingutilizing the chemical properties of the HT and HA moieties.

Microcapsules are widely used as release systems containing, forexample, self-healing agents, disinfectants, and repellants. The ruptureand eventual release of the payload is dependent on breaking the polymershell, which is typically done mechanically through scratching,puncturing, or other mechanical means directly applied to the polymersurface. The microcapsules described herein may be opened mechanicallyor chemically, as described further below.

As used herein, the term “microcapsule” is used to refer to capsulesthat are in a range of about 10 microns to 1000 microns in diameter.However, it will be appreciated that the following disclosure may beapplied to capsules having a smaller size (also referred to as“nanocapsules”).

Advantageously, HT improves the physical and thermal properties of thematerials. Polymers containing HT repeat units are quite strong, and canbe depolymerized by subjecting the polymer to chemical environments thatdebond the HT structures in the polymer. The strength of the HT unit isbelieved to proceed from the triazine ring structure, which has threebranching points. Including sufficient HT repeat units in the polymercan result in microcapsules effectively susceptible only to chemicalopening and resistant to mechanical breakage. The unique properties ofHT moieties allow for chemically triggered release of payloads undercontrolled conditions without unintended mechanical release.

Advantageously, the orthogonal-functionalized HT andorthogonal-functionalized HA allow for covalent bonding into a polymermatrix, such as a polymeric resin, thus, allowing for more sensitivedetection of cracks in the matrix. Typically, in composite containingmicrocapsules, crack propagation is used to rupture and release thepayload. By bonding the capsule to the matrix, there is a higherlikelihood of rupture due to crack propagation that does not necessarilygo through the capsule. In contrast, by bonding the capsule to thematrix, one can utilize the forces that pull the capsule apart as thematrix separates.

Advantageously, these microcapsules with walls that have HT and HAstructures can be generated with homogenous size distributions, and canbe made to avoid releasing payloads in undesirable situations, makingthe microcapsules environmentally friendly. HT and HA moieties can alsobe utilized as a functional filler for polymer composites that willincrease mechanical strength of the composite. Additionally, themicrocapsules can be incorporated at various volumes depending on theamount of payload agent(s) that might be needed, can be used as a flowcontroller replacement for nano-silica, and microcapsules' homogeneoussize allows for a controlled release of payload agent per unit area.

Advantageously, these microcapsules can find usage in multipleapplications including pharmaceutical products, insulation technologies,printed circuit boards, bezels, smart textiles, agricultural products,and consumer products such as food products, household products, andpersonal care products.

This disclosure includes chemical structures that show atomiccompositions of compounds and relative bonding arrangements of atoms ina chemical compound. Unless specifically stated, the geometricarrangement of atoms shown in the chemical structures is not intended tobe an exact depiction of the geometric arrangement of every embodiment,and those skilled in the chemical arts will recognize that compounds maybe similar to, or the same as, the illustrated compounds while havingdifferent molecular shapes or conformations. For example, the structuresdenoted herein may show bonds extending in one direction, whileembodiments of the same compound may have the same bond extending in adifferent direction. Additionally, bond lengths and angles, Van derWaals interactions, isoelectronic structures, and the like may varyamong instances of the same chemical compound. Additionally, unlessotherwise noted, the disclosed structures cover all stereoisomers,conformers, rotamers, isomers, enantiomers, of the representedcompounds.

Numbered chemical structures are numbered using numbers, or numbers andletters, in parentheses. Numbered chemical reaction schemes are numberedusing numbers, or numbers and letters, in square brackets. Unlessotherwise noted, chemical reactions are performed at ambient conditionsor under slight heating with no special atmosphere or head space, andmay be performed using standard organic solvents to manage mixproperties such as viscosity and flow index.

FIG. 1 shows formation of an exemplary payload-filled microcapsule. Theshells of the microcapsule may comprise HT and HA moieties, or acombination thereof, and the moieties may be orthogonallyfunctionalized. In FIG. 1, payload-filled microcapsules comprisingorthogonal functionality 106 are formed using an oil-in-water emulsiontechnique to create a protective polymeric shell 105 around a payloadcore.

In the example of FIG. 1, a payload 101 represents an oil phase that isdispersed into an aqueous continuous phase and stirred to begin anemulsion process. As illustrative, non-limiting examples, the payload101 (or multiple payloads) may include a perfume oil, a self-healingagent, a disinfectant, a repellant, or a combination thereof. Oneexample of a payload agent 101 that may be used is a latent curing agentsuch as N-ethylpiperazine. It will be appreciated that variouspayload(s) may be selected to provide various functionalities forvarious applications. Other possible payloads 101 could be polymerizablemolecules such as cyclic olefins, norbornene, substituted norbornene,cyclooctadiene, substituted cyclooctadiene, lactones, acrylates, acrylicacids, styrenes, isoprene, butadiene, isocyanate functional groups withhydroxyl functional groups, and epoxies. In some cases, these agents mayrequire an activator such as a catalyst and/or initiator. Additionally,solvents could be incorporated into the capsules which could be chosenfrom aprotic solvents, protic solvents, or a mixture of the two.

A cross-linking agent 102, such as formaldehyde, is reacted with apolymeric emulsifying agent 103, such as ethylene maleic anhydridecopolymer, urea (or melamine), and an orthogonal-functionalized HT smallmolecule 104 to generate a capsule wall around the payload. Othercross-linking agents 102 may be used including glutaraldehyde, di-acidchloride, and derivatives thereof. Other polymeric emulsifying agents103 may be used including whey protein isolate, sodium caseinate, asurfactant, and derivatives thereof. Particle size may be controlled byadjusting a stir speed during the reaction. For example, a faster stirspeed may result in formation (on average) of smaller (“finer”)particles than a slower stir speed.

The second part of the reaction diagram of FIG. 1, illustrates that acuring stage may be used to complete the reaction between thecross-linking agent and the polymeric emulsifying agent to form themicrocapsules or nanocapsules, depending on a stir speed. Thesenanocapsules or microcapsules are then incorporated within a polymericmatrix 105 (also referred to as a polymeric shell) to which they wouldcovalently bind. The amount of nanocapsules or microcapsules needed isempirically determined based on the rheology of the resins, the particlesize of the nanocapsule or microcapsule, and the amount needed to reachthe desired payload content for release.

In another embodiment, the orthogonal-functionalized HT small molecule104 may also be an orthogonal-functionalized hemiaminal, ahexahydrotriazine small molecule, a hemiaminal small molecule, or acombination thereof. The orthogonal-functionalized HT and HA smallmolecules may be mono-, di-, or tri-functionalized. The generalprocedure for making the microcapsule, as shown below, may be used.

Example Preparation of Microcapsule Having HT-112 and/or HA-112

The payload-containing microcapsule with walls that have HT structures,HA structures, or a combination thereof, may be prepared according tothe following exemplary process. To a stirring aqueous solutioncontaining an ethylene maleic anhydride (EMA) copolymer surfactant, urea(or melamine), and ammonium chloride (NH₄Cl), anorthogonal-functionalized HT small molecule (for example, HT-112), or anorthogonal-functionalized HA small molecule (for example, HA-112), or acombination thereof, may be added. The pH may be adjusted to about 3.5by adding NaOH and HCl (or other suitable acids and bases), followed bythe addition of an emulsifying agent (for example, a self-healingagent). The payload may be added with other ingredients, such asmonomers and/or pre-polymers, stabilizers, solvents, viscositymodifiers, odorants, colorant/dyes, blowing agents, antioxidants, orco-catalysts, or a combination thereof. Formaldehyde (or other suitablecross-linking agents) is added, which acts as a curing agent to completethe polymeric shell formation. The resulting microcapsules may besubsequently washed and sieved to remove unreacted material.

In another embodiment, the HT small molecule (for example, HT-111), HAsmall molecule (for example, HA-111), or a combination thereof may beused in making the microcapsules. The microcapsule containing, forexample, HT-111 and/or HA-111 may be made by the same process asdescribed above.

Thus, FIG. 1 illustrates a particular embodiment of a process ofproducing a microcapsule (having an encapsulated payload). The capsulemay be generated from HT small molecules, HA small molecules,orthogonal-functionalized HT small molecules, orthogonal-functionalizedHA small molecules, or a combination thereof. The payload isincorporated into a polymeric nanocapsule or microcapsule that isgenerated containing HT moieties, HA moieties, or a combination thereof.The HT- and HA-containing blocks may have orthogonal functionality,affording the ability to covalently bind to the polymeric matrix. Afterincorporation of these new microcapsules into a polymeric matrix, an enduser can rupture the capsules by various means, including using therecyclability of the HT and HA moieties. An end user may also ruptureand release the payload via scratching, puncturing, or other mechanicalmeans, or recycling of the HT and HA small molecules.

All varieties of the HA and HT small molecules described herein willparticipate in the emulsion polymerization to form the microcapsule.

Example Preparation of Microcapsule Having HT-113 and/or HA-113

To a stirring aqueous solution containing an ethylene maleic anhydride(EMA) copolymer surfactant, urea (or melamine), and ammonium chloride(NH₄Cl), an orthogonal-functionalized HT small molecule (for example,HT-113), an orthogonal-functionalized HA small molecule (for example,HA-113), or a combination thereof, may be added. The pH may be adjustedto about 3.5 by adding NaOH and HCl (or other suitable acids and bases),followed by the addition of an emulsifying agent (for example, aself-healing agent). The payload may be added with other ingredients,such as monomers and/or pre-polymers, stabilizers, solvents, viscositymodifiers, odorants, colorant/dyes, blowing agents, antioxidants, orco-catalysts, or a combination thereof. Formaldehyde is added, whichacts as a curing agent to complete the polymeric shell formation. Theresulting microcapsules may be subsequently washed and sieved to removeunreacted material.

Example Preparation of Microcapsule Having HT-114 and/or HA-114

To a stirring aqueous solution containing an ethylene maleic anhydride(EMA) copolymer surfactant, urea (or melamine), and ammonium chloride(NH₄Cl), an orthogonal-functionalized HT small molecule (for example,HT-114), an orthogonal-functionalized HA small molecule (for example,HA-114), or a combination thereof, may be added. The pH may be adjustedto about 3.5 by adding NaOH and HCl (or other suitable acids and bases),followed by the addition of an emulsifying agent (for example, aself-healing agent). The payload may be added with other ingredients,such as monomers and/or pre-polymers, stabilizers, solvents, viscositymodifiers, odorants, colorant/dyes, blowing agents, antioxidants, orco-catalysts, or a combination thereof. Formaldehyde is added, whichacts as a curing agent to complete the polymeric shell formation. Theresulting microcapsules may be subsequently washed and sieved to removeunreacted material.

As an example of an embodiment, Scheme 1 shows formation of ahexahydrotriazine small molecule HT-111 from hydroquinone 107. To asolution of hydroquinone 107 in tetrahydrofuran (THF), at a temperatureof about room temperature, is added imidazole andtert-butyldimethylsilyl chloride (TBSCl) to provide a monoprotectedhydroquinone, not shown. The protecting group may be other groups suchas a tetrydropyran group, an acetate group, or a methoxymethyl ethergroup. Those of ordinary skill in the art will recognize that otherprotecting groups and reaction conditions may be used. To a stirringsolution of the monoprotected hydroquinone is added potassium carbonate(K₂CO₃) and 1-fluoro-4-nitrobenzene in a suitable solvent to givetert-butyldimethyl(4-(4-nitrophenoxy)phenoxy)silane 108. This additionmay occur in any suitable solvent, including N-methyl-2-pyrrolidone(NMP) and dimethylformamide (DMF), at a temperature of about 80° C. toabout 100° C. The nitro group of 108 is reduced to the correspondinganiline 109, 4-(4-((tert-butyldimethylsilyl)oxy)phenoxy)aniline, withhydrazine (N₂H₄) and palladium on carbon (Pd/C). For the reduction, thePd/C catalyst, in the form of a powder, is stirred into the mixture withN₂H₄. Alternately, the Pd/C catalyst and N₂H₄ can be dispersed ordissolved in any suitable solvent to form a solution, which is thenadded to the reaction mixture. The reduction may occur in any suitablesolvent, including ethanol and NMP, at a temperature of about roomtemperature or elevated temperature, up to about 100° C.

1,3,5-tris(4-(4-((tert-butyldimethylsilyl)oxy)phenoxy)phenyl)-1,3,5-triazinane (HT-110) is then formed byreaction of aniline 109 with a formaldehyde material (i.e., formaldehydeor paraformaldehyde) in the presence of N-methyl-2-pyrrolidinone.Aniline 109 and formaldehyde are dissolved in a solvent such asN-methyl-2-pyrrolidone, and mixed. The reaction mixture is heated gentlywhile mixing. Usable solvents for the reaction include any suitablesolvents, including dipolar aprotic solvents such as, for example,N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO),N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), propylenecarbonate (PC), and propylene glycol methyl ether acetate (PGMEA). Mostpreferably, the solvent is NMP. The reaction may be performed attemperatures of about 50° C. to about 200° C.

Performing the reaction at lower temperatures, for example below about80° C., forms a hemiaminal, for example,((4-(4-((tert-butyldimethylsilyl)oxy)phenoxy)phenyl)(((4-(4-((tert-butyldimethylsilyl)oxy)phenoxy)phenyl)(((4-(4-((tert-butyldimethylsilyl)oxy)phenoxy)phenyl)amino)methyl)amino)methyl)amino)methanol(HA-110). HA-110 is shown in its hydrogen bonded form, coordinated withNMP. The reaction proceeds through the hemiaminal stage at lowtemperatures, and at higher temperatures water is eliminated as the freeamine and hydroxyl groups react to close the ring. Thus, an HA, HT, or amixture of HA and HT may be formed depending on how the reaction isperformed. If the reaction is performed for an extended time at atemperature above about 80° C., the material will be an HT. If thereaction temperature never exceeds 80° C., the material will be mostly,or entirely, HA. If the reaction is performed for a time at atemperature between about 50° C. and about 80° C., and then continued ata temperature above about 80° C. for a limited time, a mixture of HA andHT units may be formed.

Triazine HT-110 and tetra-N-butylammonium fluoride (TBAF) are dissolvedin THF, or any other suitable solvent, to perform the deprotection andprovide HT small molecule4,4′,4″-(((1,3,5-triazinane-1,3,5-triyl)tris(benzene-4,1-diyl))tris(oxy))triphenol(HT-111). This reaction may occur at temperatures of about 0° C. toabout room temperature. This HT small molecule HT-111 may be used forthe microcapsules. As mentioned above, those of ordinary skill in theart will recognize other protecting groups that may be used at earlierstages of the synthesis and subsequent reaction conditions that may beused to remove such protecting groups.

As shown in Scheme 2, and according to another embodiment, HA-110 canundergo deprotection. HA-110 and tetra-N-butylammonium fluoride (TBAF)are dissolved in THF, or any other suitable solvent, to perform thedeprotection and provide HA small molecule4-(4-((hydroxymethyl)(((4-(4-hydroxyphenoxy)phenyl)(((4-(4-hydroxyphenoxy)phenyl)amino)methyl)amino)methyl)amino)phenoxy)phenol(HA-111). This reaction may occur at temperatures of about 0° C. toabout room temperature. In Scheme 2, HA-110 is shown in its non-hydrogenbonded form. Similarly, HA-111 is shown in its non-hydrogen bonded form.

As explained above, a mixture of both HA-110 and HT-110 may be formed.In such cases, the mixture may also be deprotected according to theprocedures described herein.

It should be understood that other small molecules incorporating thehexahydrotriazine (HT) or hemiaminal (HA) core can be synthesized foruse in the embodiments described herein. In one example, an HT and an HAcan be represented by the structures

wherein the structure of formula (1) is an HT structure and thestructure of formula (2) is a HA structure. Groups K′ that may be partof the HT or HA small molecule may include the following structures:

wherein X′ and X″ are each independently selected from the groupconsisting of —OH, —O—, —NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂,—OR², and —R³, and combinations thereof, wherein R¹, R², and R³independently comprise at least 1 carbon. X′ and X″ may be an alkoxygroup, including oligo(ethylene glycol), poly(ethylene glycol), or analkene group, including vinyl and allyl.

Structures containing X′ and X″ (such as, where X′ and X″ are —OH, —O—,—NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, and —SO₂) would have protectinggroups during the synthesis of HA and HT small molecules. Suitableprotecting groups include tosyls for amines, ethynyl p-tolyl sulphones(tosylacetylene) for thiols, and tert-butyldimethylsilyl ethers foralcohols. Those of ordinary skill in the art will recognize othersuitable protecting groups, reaction conditions, and deprotecting agentsthat can be used during the synthesis of HA and HT small moleculesincorporating such groups.

Other groups K′ usable for the HT and HA small molecules describedherein may have at least one 6-carbon aromatic ring. A category of suchgroups may be represented by the structure of formula (3)

wherein L′ is selected from the group consisting of —O—, —S—, —N(R⁴)—,—N(H)—, —R⁵—, and combinations thereof, wherein R⁴ and R⁵ independentlycomprise at least 1 carbon; and wherein X′ is selected from the groupconsisting of —OH, —O—, —NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂,—OR², and —R³, and combinations thereof, wherein R¹, R², and R³independently comprise at least 1 carbon. X′ may be an alkoxy group,including oligo(ethylene glycol), poly(ethylene glycol), or an alkenegroup, including vinyl and allyl.

In an embodiment, R⁴ and R⁵ are independently selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, phenyl, and combinationsthereof. Other L′ groups include methylene (—CH₂—), isopropylidenyl(—C(Me)₂-), and fluorenylidenyl

Structures containing X′ and X″ (such as, where X′ and X″ are —OH, —O—,—NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, and —SO₂) would have protectinggroups during the synthesis of HA and HT small molecules. Suitableprotecting groups include tosyls for amines, ethynyl p-tolyl sulphones(tosyl acetylene) for thiols, and tert-butyldimethylsilyl ethers foralcohols. Those of ordinary skill in the art will recognize othersuitable protecting groups, reaction conditions, and deprotecting agentsthat can be used during the synthesis of HA and HT small moleculesincorporating such groups.

As an example of another embodiment and as shown in Scheme 3, anorthogonal-functionalized HT small molecule HT-112 may be preparedaccording to the following exemplary process. To a stirring solution ofHT small molecule HT-111 in THF and/or ether, at a temperature of about0° C. to about room temperature, is added a sodium hydride (NaH)suspension or potassium carbonate (K₂CO₃). Next, allyl chloride is addedto the stirring solution which is maintained at a temperature of about0° C. to about room temperature, and then allowed to warm to roomtemperature to give4,4′-(((5-(4-(4-(allyloxy)phenoxy)phenyl)-1,3,5-triazinane-1,3-diyl)bis(4,1-phenylene))bis(oxy))diphenol(HT-112). For this reaction, any suitable base may be used, including ahydride base or a hydroxide base. Any suitable solvent for the reactionmay be used, including ether and THF. A mixture of mono-, di-, andtri-functionalized allyl ethers may form from the reaction. The amountof mono-, di- and tri-functionalized allyl ethers can be controlled bystoichiometry and dilute conditions.

Microcapsules with orthogonal functionality at the surface thereof allowfor the ability to bind (through, for example, the allyl group) into thepolymer to increase rupture of the capsule, as described thereof.Moreover, microcapsules with orthogonal functionality can provide fordual functionality. For example, microcapsules with orthogonalfunctionality can be used for filler materials having orthogonal flameretardants on the outside of the capsule and a self-healing agent on theinside of the capsule.

As an example of another embodiment and as shown in Scheme 4, HA-111 maybe used as a precursor to prepare orthogonal-functionalized HA smallmolecules such as4-(4-((((4-(4-(allyloxy)phenoxy)phenyl)(((4-(4-hydroxyphenoxy)phenyl)amino)methyl)amino)methyl)(hydroxymethyl)amino)phenoxy)phenol (HA-112). HA-112 may be prepared according to the procedure describedabove. A mixture of mono-, di-, and tri-functionalized allyl ethers mayform from the reaction. The amount of mono-, di- and tri-functionalizedallyl ethers can be controlled by stoichiometry and dilute conditions.

The allyl-functionalized HT small molecule HT-112 and HA small moleculeHA-112 are non-limiting examples of orthogonal-functionalized HT- andHA-small molecules. Other examples of orthogonal groups (Y) includealkene-functionalized (via allyl chloride, for example),(meth)acrylate-functionalized (via (meth)acryloyl chloride, forexample), and epoxy-functionalized resveratrol (via epichlorohydrin, forexample) which can be used to react with the appropriate moiety withinthe polymeric resin. Other orthogonal groups (Y) includealkyne-functionalized (via propargyl chloride) that may be used forClick chemistry; and sulfur-functionalized (via mercaptoacetyl chlorideor thiolalkylchloride) that may be used for thiolene or vulcanizationchemistry. The thiol alkyl chloride can be protected, for example as athioacetate, for the alkylation step. Other examples of orthogonalgroups (Y) include the following structures

wherein R⁶ is X′ or X″ of the HT or HA small molecule. During formationof the HT and HA, steps such as the formation of the hexahydrotriazineshould be done at the lower end of the temperature range for compoundscontaining, for example, dioxolanone (4) or epoxide (6). Alternately,compounds containing epoxide (6) can be formed from hexahydrotriazinecompounds containing allyl group (8) by reactions known by those skilledin the art. For example, after formation of the HT compound containingan allyl group, the solvent is removed by standard techniques known tothose skilled in the art. Next, addition of meta-chloroperoxybenzoicacid (m-CPBA) to the HT compound containing an allyl group indichloromethane, provides an HT compound containing an epoxide. Standardtechniques of solvent removal should then be accomplished.

Additionally, the dioxolanone (4) may be formed after formation of thehexahydrotriazine by reaction of compounds hexahydrotriazine compoundscontaining epoxide group (6) known to those skilled in the art. Forexample, after formation of the HT compound containing the epoxide isformed (as described above), the epoxide can be converted to dioxolanoneby using NMP as solvent, catalytic ethylene glycol and carbon dioxide (2MPa), according to the general procedure of Liu, et al., BioResources,8(3), 4218-4226, 2013. Prior to the conversion to dioxolanone, standardtechniques of solvent removal should be accomplished. For other groupssuch as alcohols (10) amines (9), and thiols (11) and (12), the moietiesshould bear protecting groups prior to hexahydrotriazine formation asdescribed above.

The orthogonal-functionalized HT small molecules may be mono-, di-, andtri-functionalized. The amount of mono-, di- and tri-functionalizedorthogonal-functionalized HT small molecules can be controlled bystoichiometry and dilute conditions.

All varieties of the HT- and HA small molecules will participate in theemulsion polymerization to form the microcapsule described above.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A microcapsule, comprising: ahexahydrotriazine-based compound having the structure

a hemiaminal-based compound having the structure

or a combination thereof, wherein: at least one starred bond of thehexahydrotriazine-based compound, the hemiaminal-based compound, or acombination thereof, represents a connection to a moiety of thehexahydrotriazine-based compound, the moiety comprising

wherein: X′ and X″ are each independently selected from the groupconsisting of —OH, —O—, —NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂,—OR², —R³, and combinations thereof; L′ is selected from the groupconsisting of —O—, —S—, —N(R⁴)—, —N(H)—, and —R⁵—; and R¹, R², R³, R⁴,and R⁵ independently comprise at least 1 carbon.
 2. The microcapsule ofclaim 1, further comprising a payload.
 3. The microcapsule of claim 1,wherein one or more of R¹, R², or R³ comprises


4. The microcapsule of claim 1, wherein at least a portion of thehexahydrotriazine-based compound, the hemiaminal-based compound, or acombination thereof, is a reaction product of a formaldehyde materialand an amine.
 5. The microcapsule of claim 4, wherein the amine is anaromatic amine.
 6. The microcapsule of claim 1 further comprising arepellant.
 7. The microcapsule of claim 1, wherein each of R⁴ and R⁵ areindependently selected from the group consisting of methyl, ethyl,propyl, isopropyl, phenyl, and combinations thereof.
 8. A microcapsule,comprising: a hexahydrotriazine-based compound having the structure

a hemiaminal-based compound having the structure

or a combination thereof, wherein: at least one starred bond of thehexahydrotriazine-based compound, the hemiaminal-based compound, or acombination thereof, represents a connection to a moiety of thehexahydrotriazine-based compound, the moiety comprising

wherein: X′ is selected from the group consisting of —OH, —O—, —NH₂,—NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂, —OR², —R³, and combinationsthereof; L′ is selected from the group consisting of —O—, —S—, —N(R⁴)—,—N(H)—, and —R⁵—; and R¹, R², R³, R⁴, and R⁵ independently comprise atleast 1 carbon.
 9. The microcapsule of claim 8, further comprising apayload.
 10. The microcapsule of claim 8, wherein one or more of R¹, R²,or R³ comprises


11. The microcapsule of claim 8, wherein at least a portion of thehexahydrotriazine-based compound, the hemiaminal-based compound, or acombination thereof, is a reaction product of a formaldehyde materialand an amine.
 12. The microcapsule of claim 11, wherein the amine is anaromatic amine.
 13. The microcapsule of claim 8 further comprising arepellant.
 14. The microcapsule of claim 8, wherein each of R⁴ and R⁵are independently selected from the group consisting of methyl, ethyl,propyl, isopropyl, phenyl, and combinations thereof.
 15. A microcapsule,comprising: a hexahydrotriazine-based compound having the structure

wherein: at least one starred bond of the hexahydrotriazine-basedcompound represents a connection to a moiety of thehexahydrotriazine-based compound, the moiety comprising

wherein: X′ and X″ are each independently selected from the groupconsisting of —OH, —O—, —NH₂, —NH—, —N(R¹)H, —N(R¹)—, —SH, —S—, —SO₂,—OR², —R³, and combinations thereof; L′ is selected from the groupconsisting of —O—, —S—, —N(R⁴)—, —N(H)—, and —R⁵—; and R¹, R², R³, R⁴,and R⁵ independently comprise at least 1 carbon.
 16. The microcapsule ofclaim 15, further comprising a payload.
 17. The microcapsule of claim15, wherein one or more of R¹, R², or R³ comprises


18. The microcapsule of claim 15, wherein at least a portion of thehexahydrotriazine-based compound, is a reaction product of aformaldehyde material and an aromatic amine.
 19. The microcapsule ofclaim 15, further comprising a repellant.
 20. The microcapsule of claim15, wherein each of R⁴ and R⁵ are independently selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, phenyl, and combinationsthereof.